1. Field of the Invention
The present invention relates to an LED package structure, a dam structure thereof, and a method of manufacturing the LED package structure thereof; in particular, to an LED package structure which has multiple LED chips disposed on the top surface of the carrier and a dam structure for enclosing a resin encapsulating the LED, and to a method of manufacturing the LED package structure thereof.
2. Description of Related Art
With advancement of LED package technology, integrated circuit and heat-dissipation techniques, the LED application is becoming ever more diverse.
FIG. 1 shows a conventional LED package structure that includes a carrier 9, multiple LED chips 92 disposed on a top surface of the carrier 9, and a dam structure 94 enclosing the LED chips 92. The carrier 9 includes a conducting substrate 90, a dielectric layer D and a conductive layer 91. The LED chips 92 are connected to two sides of the conductive layer 91 by wire bonding. As shown in FIG. 1, wires 921, 922 connect the LED chips 92 to the conductive layer 91. The dam structure 94 may be a white frame enclosing the LED chips 92 and encapsulation resin is filled within (not shown in the FIG. 1). Conventional dam structure is usually made by molding. However, the molding equipment for molding the dam structure has to be modified each time when the light-emitting area of the LED package is changed so as to adjust the contour of the dam structure. It results in an increase in production cost. When the contour of the dam structure needs to be modified, such as the diameter of dam, the configuration of the molding equipment needs to be modified accordingly. Therefore, conventional dam construction formed by molding method does not have enough flexibility when the contour of the dam structure needs to be redesigned.
Another conventional technique is usually applied by using a dispenser to dispense glue material on the periphery of the LED chips 92, and the glue material undergoes curing to form the dam structure 94. This dispensing method often results in defective appearances of the dam structure 94, especially at the starting and ending portions which are prone to protuberances, often leading to the unevenness of the glue surface. The unevenness of the glue surface may further result in the color consistence when the light emitted from the LED chips 92 passes through the unevenness of glue surface. Therefore, shape inconsistency of the dam structure is a concern in mass production.
Moreover, due to restrictions of material properties of glue material, for example when using glue with a thixotropic index of 3.5, the ratio of height to width for the dam structure 94 is usually smaller than 0.8, and is typically ranged between 0.6 and 0.7. Namely, the appearance of the dam structure 94 is relatively fat and wide. However, the number of LED chips 92 that can be disposed in the light-emitting area are decreased. Therefore, the overall design for LED package is influenced. Additionally, the wire is likely to be pressed by the fat and wide dam structure 94 such that wire malfunction is occurred. (e.g., current leakage.) For example, the wire 921 on the right of FIG. 1 is prone to be pressed by the dam structure 94 which appearance is fat and wide.
Additionally, an optical lens is usually added on LED package for modifying the lighting profile. When constructing the dam structure, the outer diameter of the dam structure must be substantially equal to the inner diameter of optical lens. Therefore, when the outer diameter of the dam is too large, the number of LED chips that can be placed within the light-emitting area will be affected, and the optical lens with standard scale cannot engage with all kinds of the dam structures having different outer diameter.
Hence, the present inventor believes the above mentioned disadvantages can be overcome, and through devoted research combined with application of theory, finally proposes the present disclosure which has a reasonable design and effectively improves upon the above mentioned disadvantages.